This report, digital geodatabase, and the accompanying set of plottable geologic maps were prepared to provide an updated and spatially accurate geologic framework for the southern Oregon coast between Bandon, Coquille, and Sunset Bay in western Coos County (Figure 1). Geologic mapping summarized here represents one part of a multi-year project to map the Oregon coast from the California border north to Coos Bay (Figure 2). The project is a high priority of the Oregon Geologic Map Advisory Committee (OGMAC) and was supported in part during 2014 and 2015 by the U.S. Geological Survey (USGS) STATEMAP component of the National Cooperative Geologic Mapping Program under assistance award G14AC00165. Matching funds were provided by the Oregon Department of Geology and Mineral Industries (DOGAMI). The core product of this study is an Esri ArcGIS™ ArcMap™ 10.1 format geodatabase that combines new and existing mapping in a digital format consistent with the digital statewide Oregon Geologic Data Compilation database (OGDC-5, Ma and others, 2009). Both bedrock and surficial geologic interpretations can be recovered from the geodatabase. It contains spatial information about geologic units and structures, and basic data about each geologic unit such as age, lithology, mineralogy, and structure. Digitization at scales of 1:8,000 or better was accomplished using georeferenced lidar base layers. The geodatabase is supported by this report describing the geology in detail, and digital appendices with geochemical, geochronological, structural, and water well data. Four plottable geologic maps, showing the distribution of contrasting bedrock lithologies, critical structural relationships, and surficial geology, cover the Bill Peak 7.5′ quadrangle (Plate 1), the Coquille 7.5′ quadrangle (Plate 2), the Bullards and Riverton 7.5′ quadrangles (Plate 3), and the Cape Arago 7.5′ quadrangle (Plate 4) at a scale of 1:24,000. These maps refine our understanding of geologic conditions that control the distribution, quantity, and quality of groundwater resources, the distribution of terrain susceptible to landslides, the nature of seismic hazards, and the distribution of potential aggregate sources and other mineral resources. The geodatabase provides a basis for future geologic, geohydrologic, and geohazard studies in this part of the southern Oregon coast.

PLATES

Note: Map plates PDFs are in geospatial PDF format, allowing you to turn on and off layers in the map frame and to find geographic coordinates in the PDF if you have the free plugin for Adobe Reader. Learn more about the geospatial PDFs here.